Mixture of dyes for black dye donor for thermal color proofing

ABSTRACT

A black dye-donor element for thermal dye transfer comprising a support having thereon a dye layer comprising a mixture of at least one cyan, magenta and yellow dyes dispersed in a polymeric binder, at least one of the cyan dyes having the formula: ##STR1## and at least one of the yellow dyes having the formula: ##STR2## and at least one of the magenta dyes having the formula: ##STR3##

This invention relates to use of a mixture of cyan, yellow and magentadyes in a black dye-donor element for thermal dye transfer imaging whichcan be used in a four-color proofing system that accurately representsthe hue of a printed color image obtained from a printing press.

In order to approximate the appearance of continuous-tone (photographic)images via ink-on-paper printing, the commercial printing industryrelies on a process known as halftone printing. In halftone printing,color density gradations are produced by printing ink as patterns of"dots" of varying sizes, but of constant color density, instead ofvarying the color density continuously as is done in photographicprinting.

There is an important commercial need to obtain a color proof imagebefore a printing press run is made which will emulate the final printedimage as closely as possible. Such a pre press proof will be used as aguide to the press operator during the set-up and calibration of theprinting press. It is desired that the color proof will accuratelyrepresent at least the neutral (gray) and color tone scales of theprints obtained on the printing press. In many cases, it is alsodesirable that the color proof accurately represent the image qualityand halftone pattern of the prints obtained on the printing press.Traditionally, such color separation proofs have involved silver halidephotographic, high-contrast lithographic systems or non-silver halide(for example the Signature® electrophotographic analog proofing systemavailable from Eastman Kodak) light-sensitive systems which require manyexposure and processing steps before a final, full-color proof isassembled.

Colorants that are used in the printing industry are insoluble pigmentsdispersed in a suitable carrier liquid to make an ink. In particular,carbon is often used in such a black ink and results in fairly uniformabsorbance across the visible spectrum. In thermal transfer colorprinting systems that use diffusible dyes it is often difficult to finda blend of two or more dyes which yields both uniform neutral (black)color and fulfills the other requirements of the printing system such astransfer efficiency and donor storage stability.

In U.S. patent application Ser. No. 514,643, filed Apr. 25, 1990, ofDeBoer, a process is described for producing a direct digital, halftonecolor proof of an original image on a dye-receiving element by means oflaser thermal dye transfer. The proof can then be used to represent aprinted color image obtained from a printing press. The processdescribed therein comprises:

a) generating a set of electrical signals which is representative of theshape and color scale of an original image;

b) contacting a dye-donor element comprising a support having thereon adye layer and an infrared-absorbing material with a first dye-receivingelement comprising a support having thereon a polymeric, dyeimage-receiving layer;

c) using the signals to imagewise-heat by means of a diode laser thedye-donor element, thereby transferring a dye image to the firstdye-receiving element; and

d) retransferring the dye image to a second dye image-receiving elementwhich has the same substrate as the printed color image.

In the above process, multiple dye-donors are used to obtain a completerange of colors in the proof. For example, for a full-color proof, fourcolors: cyan, magenta, yellow and black are normally used.

By using the above process, the image dye is transferred by heating thedye-donor containing the infrared-absorbing material with the diodelaser to volatilize the dye, the diode laser beam being modulated by theset of signals which is representative of the shape and color of theoriginal image, so that the dye is heated to cause volatilization onlyin those areas in which its presence is required on the dye-receivinglayer to reconstruct the original image.

Similarly, a thermal transfer proof can be generated by using a thermalhead in place of a diode laser as described in U.S. Pat. No. 4,923,846.Commonly available thermal heads are not capable of generating halftoneimages of adequate resolution but can produce high quality continuoustone proof images which are satisfactory in many instances. U.S. Pat.No. 4,923,846 also discloses the choice of mixtures of dyes for use inthermal imaging proofing systems. The dyes are selected on the basis ofvalues for hue error and turbidity. The Graphic Arts TechnicalFoundation Research Report No. 38, "Color Material" (58-(5) 293-301,1985 gives an account of this method.

An alternative and more precise method for color measurement andanalysis uses the concept of uniform color space known as CIELAB inwhich a sample is analyzed mathematically in terms of itsspectro-photometric curve, the nature of the illuminant under which itis viewed and the color vision of a standard observer. For a discussionof CIELAB and color measurement, see "Principles of Color Technology",2nd Edition, p.25-110, Wiley-Interscience and "Optical RadiationMeasurements", Volume 2, p.33-145, Academic Press.

In using CIELAB, colors can be expressed in terms of three parameters:L*, a* and b*, where L* is a lightness function, and a* and b* define apoint in color space. Thus, a plot of a* v. b* values for a color samplecan be used to accurately show where that sample lies in color space,i.e., what its hue is. This allows different samples to bequantitatively compared.

In color proofing in the printing industry, it is important to be ableto match the proofing ink references provided by the InternationalPrepress Proofing Association. These ink references are density patchesmade with standard 4-color process inks and are known as SWOP(Specifications Web Offset Publications) Color References. Foradditional information on color measurement of inks for web offsetproofing, see Advances in Printing Science and Technology", Proceedingsof the 19th International Conference of Printing Research Institutes,Eisenstadt, Austria, June 1987, J. T. Ling and R. Warner, p.55.

Thus, this invention relates to the use of a mixture of cyan, yellow andmagenta dyes for thermal dye transfer imaging to approximate a hue matchof the black SWOP Color Reference. The mixtures of dyes described inthis invention provide a closer hue match to the SWOP standard andbetter transfer density than the preferred dye mixtures of U.S. Pat. No.4,923,846.

In U.S. Pat. No. 4,816,435, a combination of thermally transferrabledyes is disclosed for use in producing black images. The dye typesdisclosed are di- and tri-cyanovinylanilines (for the yellow and magentarespectively) and phenol-based indoaniline cyan dyes. There is a problemwith using these dyes in dye-donors in that the storage stability is notas good as one would like it to be. It would be desirable to provide ablack dye-donor with good storage stability.

In JP 01/136,787, a combination of thermally-transferrable dyes isdisclosed for use in producing black images. Quinophthalone,dicyanovinyl aniline and azopyridone yellow dyes are described alongwith imidazolylazonaniline magenta and phenol-based indoaniline cyandyes. Here again, there is a problem with using these dyes in dye-donorsin that the storage stability is not as good as one would like it to be.

Accordingly, this invention relates to a black dye-donor element forthermal dye transfer comprising a support having thereon a dye layercomprising a mixture of cyan, yellow and magenta dyes dispersed in apolymeric binder, at least one of the cyan dyes having the formula:##STR4## wherein: R¹ and R² each independently represents hydrogen; analkyl group having from 1 to about 10 carbon atoms; a cycloalkyl grouphaving from about 5 to about 7 carbon atoms; allyl; or such alkyl,cycloalkyl or allyl groups substituted with one or more groups such asalkyl, aryl, alkoxy, aryloxy, amino, halogen, nitro, cyano, thiocyano,hydroxy, acyloxy, acyl, alkoxycarbonyl, aminocarbonyl,alkoxycarbonyloxy, carbamoyloxy, acylamido, ureido, imido,alkylsulfonyl, arylsulfonyl, alkylsulfonamido, arylsulfonamido,alkylthio, arylthio, trifluoromethyl, etc., e.g., methyl, ethyl, propyl,isopropyl, butyl, pentyl, hexyl, methoxyethyl, benzyl,2-methanesulfonamidoethyl, 2-hydroxyethy1,2-cyanoethyl,methoxycarbonylmethyl, cyclohexyl, cyclopentyl, phenyl, pyridyl,naphthyl, thienyl, pyrazolyl, p-tolyl, p-chlorophenyl,m-(N-methyl-sulfamoyl)phenylmethyl, methylthio, butylthio, benzylthio,methanesulfonyl, pentanesulfonyl, methoxy, ethoxy,2-methane-sulfonamidoethyl, 2-hydroxyethyl, 2-cyanoethyl,methoxy-carbonylmethyl, imidazolyl, naphthyloxy, furyl, p-tolylsulfonyl,p-chlorophenylthio, m-(N-methyl sulfamoyl)phenoxy, ethoxy-carbonyl,methoxyethoxycarbonyl, phenoxy-carbonyl, acetyl, benzoyl,N,N-dimethyl-carbamoyl, dimethylamino, morpholino, anilino, pyrrolidinoetc.; with the proviso that R¹ and R² cannot both be hydrogen;

or R¹ and R² can be joined together to form, along with the nitrogen towhich they are attached, a 5- to 7-membered heterocyclic ring such asmorpholine or pyrrolidine;

or either or both of R¹ and R² can be combined with an R³ to form a 5-to 7-membered heterocyclic ring;

each R³ independently represents substituted or unsubstituted alkyl,cycloalkyl or allyl as described above for R¹ and R² ; alkoxy, aryloxy,halogen, thiocyano, acylamido, ureido, alkylsulfonamido,arylsulfonamido, alkylthio, arylthio or trifluoromethyl;

or any two of R³ may be combined together to form a 5- or 6-memberedcarbocyclic or heterocyclic ring;

or one or two of R³ may be combined with either or both of R¹ and R² tocomplete a 5- to 7-membered ring;

m is an integer of from 0 to 4;

R⁴ represents hydrogen or an electron withdrawing group such as cyano,alkoxycarbonyl, aminocarbonyl, alkylsulfonyl, arylsulfonyl, acyl, nitro,etc.;

R⁵ represents an electron withdrawing group such as those listed abovefor R⁴ ; an aryl group having from about 6 to about 10 carbon atoms; ahetaryl group having from about 5 to about 10 atoms; or such aryl orhetaryl groups substituted with one or more groups such as are listedabove for R¹ and R² ;

R⁶ and R⁷ each independently represents an electron withdrawing groupsuch as those described above for R⁴ ; or R⁶ and R⁷ may be combined toform the residue of an active methylene compound such as apyrazolin-5-one, a pyrazoline-3,5-dione, a thiohydantoin, a barbituricacid, a rhodanine, a furanone, an indandione, etc.,

and at least one of the yellow dyes having the formula: ##STR5##wherein: R⁸ represents the same groups as R¹ above; an aryl group offrom about 6 to about 10 carbon atoms, such as phenyl, 1 naphthyl, etc.;a hetaryl group of from about 5 to about 10 atoms, such as 1-quinolyl,2-thienyl, etc.; or such aryl and hetaryl groups substituted with groupsas described above;

R⁹ and R¹⁰ each independently represents hydrogen; R⁸ ; cyano; acyloxysuch as acetoxy, phenacyloxy, etc.; alkoxy of 1 to about 6 carbon atomssuch as ethoxy, i-propoxy, etc.; halogen such as fluorine, chlorine orbromine; or alkoxycarbonyl such as methoxycarbonyl, butoxycarbonyl,etc.;

or any two of R⁸, R⁹ and R¹⁰ together represent the atoms necessary tocomplete a 5- to 7-membered ring;

R¹¹ represents the same groups as R⁸ ;

G represents a substituted or unsubstituted alkyl, cycloalkyl or allylgroup as described above for R⁸, NR¹² R¹³ or OR¹⁴ ;

R¹² and R¹³ each independently represents hydrogen, acyl or R⁸, with theproviso that R¹² and R¹³ cannot both be hydrogen at the same time;

or R¹² and R¹³ together represent the atoms necessary to complete a 5-to 7-membered ring;

R¹⁴ represents alkyl, cycloalkyl or allyl groups as in R¹ above, or arylor hetaryl as in R⁸ above;

X represents C(R¹⁸)(R¹⁹), S, O or NR¹⁸ ;

R¹⁸ and R¹⁹ each independently represents the same groups as R⁸ ;

or R¹⁸ and R¹⁹ together represent the atoms necessary to complete a 5-to 7-membered ring; and

Y represents the atoms necessary to complete a 5- or 6-membered ringwhich may be fused to another ring system;

and at least one of the magenta dyes having the formula: ##STR6##wherein: R¹⁵ represents hydrogen or a substituted or unsubstituted alkylor allyl group of from 1 to about 10 carbon atoms, such as those listedabove for R¹ ;

Q is R¹⁵, an alkoxy group of from 1 to about 4 carbon atoms or takentogether with R¹⁶ represents the atoms which form a 5- or 6-memberedheterocyclic ring;

R¹⁶ is a substituted or unsubstituted alkyl or allyl group of from 1 toabout 10 carbon atoms, such as those listed above for R¹, or can becombined with Q as described above;

R²⁰ is a substituted or unsubstituted alkyl group of from 1 to about 10carbon atoms such as those listed above for R¹, or a substituted orunsubstituted aryl group of from about 6 to about 10 carbon atoms, suchas those listed above for R⁸ ;

J is CO, CO₂, --SO₂ -- or CONR²¹ --;

R¹⁷ is a substituted or unsubstituted alkyl or allyl group of from 1 toabout 10 carbon atoms, such as those listed above for R¹, or asubstituted or unsubstituted aryl group of from about 6 to about 10carbon atoms, such as those listed above for R^(8;) and

R²¹ is hydrogen or R²⁰.

In a preferred embodiment for compounds according to formula I employedin the invention, R⁴, R⁶ and R⁷ are cyano. In another preferredembodiment for compounds according to formula I employed in theinvention, R¹ is C₂ H₅, C₂ H₄ OH, or n-C₃ H₇. In yet another preferredembodiment for compounds according to formula I employed in theinvention, R² is C₂ H₅ or n-C₃ H₇. In yet still another preferredembodiment for compounds according to formula I employed in theinvention, R³ is hydrogen, OC₂ H₅, CH₃ or NHCOCH₃. In another preferredembodiment for compounds according to formula I employed in theinvention, R⁵ is p-C₆ H₄ Cl, m-C₆ H₄ NO₂ or naphthyl.

Compounds included within the scope of formula I employed in theinvention include the following:

    __________________________________________________________________________     ##STR7##                                                                     Compound                                                                            R.sup.1   R.sup.2                                                                           R.sup.3                                                                             R.sup.5                                             __________________________________________________________________________    I-1   C.sub.2 H.sub.5                                                                         C.sub.2 H.sub.5                                                                   CH.sub.3                                                                            C.sub.6 H.sub.5                                     I-2   C.sub.2 H.sub.5                                                                         C.sub.2 H.sub.5                                                                   H     C.sub.6 H.sub.5                                     I-3   C.sub.2 H.sub.4 OH                                                                      C.sub.2 H.sub.5                                                                   CH.sub.3                                                                            C.sub.6 H.sub.5                                     I-4   C.sub.2 H.sub.5                                                                         C.sub.2 H.sub.5                                                                   OC.sub.2 H.sub.5                                                                    C.sub.6 H.sub.5                                     I-5   n-C.sub.3 H.sub.7                                                                       n-C.sub.3 H.sub.7                                                                 NHCOCH.sub.3                                                                        C.sub.6 H.sub.5                                     I-6   C.sub.2 H.sub.5                                                                         C.sub.2 H.sub.5                                                                   CH.sub.3                                                                            o-C.sub.6 H.sub.4 OCH.sub.3                         I-7   C.sub.2 H.sub.5                                                                         C.sub.2 H.sub.5                                                                   CH.sub.3                                                                            p-C.sub.6 H.sub.4 OCH.sub.3                         I-8   C.sub.2 H.sub.5                                                                         C.sub.2 H.sub.5                                                                   CH.sub.3                                                                            p-C.sub.6 H.sub.4 Cl                                I-9   C.sub.2 H.sub.5                                                                         C.sub.2 H.sub.5                                                                   CH.sub.3                                                                            m-C.sub.6 H.sub.4 NO.sub.2                          I-10  C.sub.2 H.sub.5                                                                         C.sub.2 H.sub.5                                                                   CH.sub.3                                                                             ##STR8##                                           I-11  C.sub.2 H.sub.5                                                                         C.sub.2 H.sub.5                                                                   CH.sub.3                                                                             ##STR9##                                           I-12  C.sub.2 H.sub.5                                                                         C.sub.2 H.sub.5                                                                   CH.sub.3                                                                             ##STR10##                                          I-13  C.sub.2 H.sub.5                                                                         C.sub.2 H.sub.5                                                                   H                                                                                    ##STR11##                                          I-14  C.sub.2 H.sub.5                                                                         C.sub.2 H.sub.5                                                                   CH.sub.3                                                                            p-C.sub.6 H.sub.4 F                                 I-15  C.sub.2 H.sub.5                                                                         C.sub.2 H.sub.5                                                                   CH.sub.3                                                                            o-C.sub.6 H.sub.4 Cl                                I-16  C.sub.2 H.sub.5                                                                         C.sub.2 H.sub.5                                                                   CH.sub.3                                                                            p-C.sub.6 H.sub.4 CN                                I-17  C.sub.2 H.sub.5                                                                         C.sub.2 H.sub.5                                                                   CH.sub.3                                                                            3,4-C.sub.6 H.sub.3 Cl.sub.2                        I-18  C.sub.2 H.sub.5                                                                         C.sub.2 H.sub.5                                                                   CH.sub.3                                                                            2,4-C.sub.6 H.sub.3 Cl.sub.2                        I-19  C.sub.2 H.sub.5                                                                         C.sub.2 H.sub.5                                                                   CH.sub.3                                                                             ##STR12##                                          I-20  C.sub.2 H.sub.5                                                                         C.sub.2 H.sub.5                                                                   CH.sub.3                                                                             ##STR13##                                          I-21  C.sub.2 H.sub.5                                                                         C.sub.2 H.sub.5                                                                   CH.sub.3                                                                             ##STR14##                                          I-22  C.sub.2 H.sub.4 OH                                                                      C.sub.2 H.sub.5                                                                   CH.sub.3                                                                            p-C.sub.6 H.sub.4 Cl                                I-23  C.sub.2 H.sub.4 NHSO.sub.2 CH.sub.3                                                     C.sub.2 H.sub.5                                                                   CH.sub.3                                                                            p-C.sub.6 H.sub.4 Cl                                I-24                                                                                 ##STR15##                                                              I-25                                                                                 ##STR16##                                                              I-26                                                                                 ##STR17##                                                              I-27                                                                                 ##STR18##                                                              __________________________________________________________________________

The above dyes may be prepared analogously to the method described inExample 1 below.

In another preferred embodiment of the invention Y in the abovestructural formula II represents atoms to complete an indolylidene ring.In another preferred embodiment, G is N(CH₃)₂ or CH₃. In still anotherpreferred embodiment, X is C(CH₃)₂ or O. In yet still another preferredembodiment, R⁸ is C₂ H₅ or CH₃ and R¹¹ is C₆ H₅. In still anotherpreferred embodiment, R⁹ and R¹⁰ are each hydrogen

The compounds of formula II employed in the invention above may beprepared by any of the processes disclosed in U. S. Pat. No. 4,757,046,the disclosure of which is hereby incorporated by reference.

Compounds included within the scope of formula II employed in theinvention include the following:

    __________________________________________________________________________     ##STR19##                                                                    Cmpd                                                                              X    G     R.sup.8 R.sup.9                                                                            R.sup.10                                                                          R.sup.11                                      __________________________________________________________________________    II-1                                                                              C(CH.sub.3).sub.2                                                                  N(CH.sub.3).sub.2                                                                   C.sub.2 H.sub.5                                                                       H    H   C.sub.6 H.sub.5                               II-2                                                                              C(CH.sub.3).sub.2                                                                  CH.sub.3                                                                            CH.sub.3                                                                              H    H   C.sub.6 H.sub.5                               II-3                                                                              S    CH.sub.3                                                                            CH.sub.3                                                                              H    H   C.sub.6 H.sub.5                               II-4                                                                              S    N(CH.sub.3).sub.2                                                                   C.sub.2 H.sub.5                                                                       H    H   C.sub.2 H.sub.5                               II-5                                                                              O    CH.sub.3                                                                            CH.sub.3                                                                              H    H   C.sub.6 H.sub.5                               II-6                                                                              C(CH.sub.3).sub.3                                                                  NHCOCH.sub.3                                                                        CH.sub.3                                                                              H    H   C.sub.6 H.sub.5                               II-7                                                                              C(CH.sub.3).sub.2                                                                  OC.sub.2 H.sub.5                                                                    C.sub.3 H.sub.7                                                                       H    H   C.sub.6 H.sub.4 -4-CO.sub. 2 CH.sub.3         II-8                                                                              C(CH.sub.3).sub.2                                                                  N(CH.sub.3).sub.2                                                                   C.sub.2 H.sub.4Cl                                                                     H    CH.sub.3                                                                          C.sub.6 H.sub.5                               II-9                                                                              O    OC.sub.2 H.sub.5                                                                    CH.sub.3                                                                              H    H   C.sub.6 H.sub.5                               II-10                                                                             S    NHCOCH.sub.3                                                                        CH.sub.3                                                                              OCH.sub.3                                                                          H   CH.sub.3                                      II-11                                                                             C(CH.sub.3).sub.2                                                                  N(CH.sub.3).sub.2                                                                   CH.sub.3                                                                              CH.sub.3                                                                           H   C.sub.6 H.sub.5                               II-12                                                                             C(CH.sub.3).sub.2                                                                  OCH.sub.3                                                                           CH.sub.3                                                                              CH.sub.3                                                                           H   C.sub.6 H.sub.5                               II-13                                                                             C(CH.sub.3).sub.2                                                                  NHCOCH.sub.3                                                                        CH.sub.3                                                                              CH.sub.3                                                                           H   C.sub.6 H.sub.5                               II-14                                                                             C(CH.sub.3).sub.2                                                                  N(CH.sub.3).sub.2                                                                   C.sub.2 H.sub.5                                                                       CH.sub.3                                                                           H   C.sub.6 H.sub.5                               II-15                                                                             C(CH.sub.3).sub.2                                                                  OC.sub.3 H.sub.7 -i                                                                 C.sub.2 H.sub.5                                                                       CH.sub.3                                                                           H   C.sub.6 H.sub.4 -3Cl                          II-16                                                                             C(CH.sub.3).sub.2                                                                  NHCOCH.sub.3                                                                        C.sub.2 H.sub.5                                                                       CH.sub.3                                                                           H   C.sub.6 H.sub.5                               II-17                                                                             C(CH.sub.3).sub.2                                                                  N(CH.sub.3).sub.2                                                                   CH.sub.3                                                                              CO.sub.2 CH.sub.3                                                                  H   C.sub.2 H.sub.5                               II-18                                                                             C(CH.sub.3).sub.2                                                                  N(CH.sub.3).sub.2                                                                   CH.sub.2 CH.sub.2 OH                                                                  H    H   C.sub.6 H.sub.5                               II-19                                                                             NCH.sub.3                                                                          N(CH.sub.3).sub.2                                                                   CH.sub.3                                                                              H    OCH.sub.3                                                                         CH.sub.2 CH.sub.2 OH                          II-20                                                                             C(CH.sub.3).sub.2                                                                  N(CH.sub.3).sub.2                                                                   CH.sub.2 CONHCH.sub.3                                                                 H    H   C.sub.6 H.sub.5                               II-21                                                                             O    CH.sub.3                                                                            C.sub.2 H.sub.5                                                                       H    H   C.sub.6 H.sub.5                               __________________________________________________________________________

In a preferred embodiment for compounds according to formula IIIemployed in the invention, R¹⁵ and R¹⁶ are each C₃ H₇, Q is H, J is CO,R²⁰ is CH₃ and R¹⁷ is 3-CH₂ CO₂ C₂ H₅, In another preferred embodimentof the invention, R¹⁵ and R¹⁶ are each C₃ H₇, Q is H, J is CO, R²⁰ isCH₃ and R¹⁷ is CH₂ CH═CH₂.

The compounds of formula III above employed in the invention may beprepared by any of the processes disclosed in U.S. pat. No. 4,097,475the disclosure of which is hereby incorporated by reference.

Magenta dyes included within the scope of formula III include thefollowing:

    __________________________________________________________________________     ##STR20##                                                                    Dye R.sup.15                                                                             R.sup.16                                                                           Q        R.sup.17 R.sup.20                                                                           J                                      __________________________________________________________________________    III-1                                                                             n-C.sub.3 H.sub.7                                                                    n-C.sub.3 H.sub.7                                                                  H        CH.sub.2 CO.sub.2 C.sub.2 H.sub.5                                                      CH.sub.3                                                                           CO                                     III-2                                                                             H      C.sub.2 H.sub.5                                                                    OCH.sub.3                                                                              CH.sub.2 CO.sub.2 C.sub.2 H.sub.5                                                      CH.sub.3                                                                           CO                                     III-3                                                                             C.sub.2 H.sub.5                                                                      C(CH.sub.3).sub.2 CH.sub.2 CH(CH.sub.3)                                                     C.sub.2 H.sub.5                                                                        C.sub.2 H.sub.5                                                                    CO                                     III-4                                                                             C.sub.2 H.sub.5                                                                      C.sub.2 H.sub.5                                                                    H        CH.sub.2 COCH.sub.3                                                                    CH.sub.3                                                                           CO                                     III-5                                                                             n-C.sub.3 H.sub.7                                                                    C.sub.2 H.sub.5                                                                    H        CH.sub.2 CO.sub.2 CH.sub.3                                                             C.sub.2 H.sub.5                                                                    CO                                     III-6                                                                             CH.sub.3                                                                             CH.sub.3                                                                           H        CH.sub.2 COCH.sub.3                                                                    CH.sub.3                                                                           SO.sub.2                               III-7                                                                             H      n-C.sub.3 H.sub.7                                                                  OC.sub.2 H.sub.5                                                                       CH.sub.2 CO.sub.2 CH.sub.3                                                             C.sub.2 H.sub.5                                                                    CO                                     III-8                                                                             C.sub.2 H.sub.5                                                                      C.sub.2 H.sub.5                                                                    H        CH.sub.2 COCH.sub.3                                                                    (CH.sub.3).sub.3 C                                                                 CO                                     III-9                                                                             n-C.sub.3 H.sub.7                                                                    n-C.sub.3 H.sub.7                                                                  H        CH.sub.2 CN                                                                            C.sub.2 H.sub.5                                                                    SO.sub.2                               III-10                                                                            CH.sub.3                                                                             CH.sub.3                                                                           H        C.sub.6 H.sub.13                                                                       CH.sub.3                                                                           CO                                     III-11                                                                            CH.sub.3                                                                             CH.sub.3                                                                           H        CH.sub.2 COCH.sub.3                                                                    C.sub.6 H.sub.5                                                                    CO                                     III-12                                                                            H      CH.sub.3                                                                           OCH.sub.3                                                                              CH.sub.2 COCH.sub.3                                                                    C.sub.6 H.sub.5                                                                    CO                                     III-13                                                                            C.sub.6 H.sub.5 (CH.sub.2).sub.2                                                     C.sub.2 H.sub.5                                                                    H        CH.sub.2 CO.sub.2 CH.sub.3                                                             CH.sub.3                                                                           CO                                     III-14                                                                            H      C.sub.2 H.sub.5                                                                    OCH.sub.2 C.sub.6 H.sub.5                                                              C.sub.6 H.sub.5                                                                        C.sub.2 H.sub.5                                                                    CO                                     III-15                                                                            CH.sub.3 O(CH.sub.2).sub.2                                                           CH.sub.3                                                                           H        CH.sub.2 CN                                                                            n-C.sub.3 H.sub.7                                                                  CO                                     III-16                                                                            C.sub.2 H.sub.5                                                                      C.sub.2 H.sub.5                                                                    H        CH.sub.2 COCH.sub.3                                                                    CH.sub.3                                                                           CON(CH.sub.3)                          III-17                                                                            H      n-C.sub.3 H.sub.7                                                                  O(CH.sub.2).sub.2 OCH.sub.3                                                            CH.sub.3 CH.sub.3                                                                           CO                                     III-18                                                                            C.sub.6 H.sub.5 CH.sub.2                                                             C.sub.2 H.sub.5                                                                    H        CH.sub.2 C.sub.6 H.sub.5                                                               CH.sub.3                                                                           CO.sub.2                               III-19                                                                            n-C.sub.3 H.sub.7                                                                    n-C.sub.3 H.sub.7                                                                  H        CH.sub.2 CHCH.sub.2                                                                    CH.sub.3                                                                           CO                                     __________________________________________________________________________

The use of dye mixtures in the dye-donor of the invention permits a wideselection of hue and color that enables a close hue match to a varietyof printing inks and also permits easy transfer of images one or moretimes to a receiver if desired. The use of dyes also allows easymodification of image density to any desired level. The dyes of thedye-donor element of the invention may be used at a coverage of fromabout 0.05 to about 1 g/m².

The dyes in the dye-donor of the invention are dispersed in a polymericbinder such as a cellulose derivative, e.g., cellulose acetate hydrogenphthalate, cellulose acetate, cellulose acetate propionate, celluloseacetate butyrate, cellulose triacetate or any of the materials describedin U.S. Pat. No. 4,700,207; a polycarbonate; polyvinyl acetate;poly(styrene-co-acrylonitrile); a poly(sulfone) or a poly(phenyleneoxide). The binder may be used at a coverage of from about 0.1 to about5 g/m².

The dye layer of the dye-donor element may be coated on the support orprinted theron by a printing technique such as a gravure process.

Any material can be used as the support for the dye-donor element of theinvention provided it is dimensionally stable and can withstand the heatof the laser or thermal head. Such materials include polyesters such aspoly(ethylene terephthalate); polyamides; polycarbonates; celluloseesters such as cellulose acetate; fluorine polymers such aspolyvinylidene fluoride orpoly(tetrafluoroethylene-co-hexafluoropropylene); polyethers such aspolyoxymethylene; polyacetals; polyolefins such as polystyrene,polyethylene, polypropylene or methylpentene polymers; and polyimidessuch as polyimide-amides and polyether imides. The support generally hasa thickness of from about 5 to about 200 μm. It may also be coated witha subbing layer, if desired, such as those materials described in U.S.Pat. Nos. 4,695,288 or 4,737,486.

The reverse side of the dye-donor element may be coated with a slippinglayer to prevent the printing head from sticking to the dye-donorelement Such a slipping layer would comprise either a solid or liquidlubricating material or mixtures thereof, with or without a polymericbinder or a surface active agent. Preferred lubricating materialsinclude oils or semicrystalline organic solids that melt below 100° C.such as poly(vinyl stearate), beeswax, perfluorinated alkyl esterpolyethers, poly(capro-lactone), silicone oil,poly(tetrafluoroethylene), carbowax, poly(ethylene glycols), or any ofthose materials disclosed in U.S. Pat. Nos. 4,717,711; 4,717,712;4,737,485; and 4,738,950. Suitable polymeric binders for the slippinglayer include poly(vinyl alcohol-co-butyral), poly(vinylalcohol-co-acetal), poly(styrene), poly(vinyl acetate), celluloseacetate butyrate, cellulose acetate propionate, cellulose acetate orethyl cellulose.

The amount of the lubricating material to be used in the slipping layerdepends largely on the type of lubricating material, but is generally inthe range of about 0.001 to about 2 g/m². If a polymeric binder isemployed, the lubricating material is present in the range of 0.1 to 50weight %, preferably 0.5 to 40, of the polymeric binder employed.

The dye-receiving element that is used with the dye-donor element of theinvention usually comprises a support having thereon a dyeimage-receiving layer. The support may be a transparent film such as apoly(ether sulfone), a polyimide, a cellulose ester such as celluloseacetate, a poly(vinyl alcohol-co-acetal) or a poly(ethyleneterephthalate). The support for the dye-receiving element may also bereflective such as baryta-coated paper, polyethylene-coated paper, anivory paper, a condenser paper or a synthetic paper such as duPontTyvek®. Pigmented supports such as white polyester (transparentpolyester with white pigment incorporated therein) may also be used.

The dye image-receiving layer may comprise, for example, apolycarbonate, a polyurethane, a polyester, polyvinyl chloride,poly(styrene-co-acrylonitrile), poly(caprolactone), a poly(vinyl acetal)such as poly(vinyl alcohol co-butyral), poly(vinyl alcohol-co-benzal),poly(vinyl alcohol-co-acetal) or mixtures thereof. The dyeimage-receiving layer may be present in any amount which is effectivefor the intended purpose. In general, good results have been obtained ata concentration of from about 1 to about 5 g/m².

As noted above, the dye-donor elements of the invention are used to forma dye transfer image. Such a process comprises imagewise-heating adye-donor element as described above and transferring a dye image to adye-receiving element to form the dye transfer image.

The dye-donor element of the invention may be used in sheet form or in acontinuous roll or ribbon. If a continuous roll or ribbon is employed,it may have only the dyes thereon as described above or may havealternating areas of other different dyes or combinations, such assublimable cyan and/or yellow and/or black or other dyes. Such dyes aredisclosed in U.S. Pat. Nos. 4,541,830, the disclosure of which is herebyincorporated by reference. Thus, one-, two-, three- or four-colorelements (or higher numbers also) are included within the scope of theinvention.

Thermal printing heads which can be used to transfer dye from thedye-donor elements of the invention are available commercially. Therecan be employed, for example, a Fujitsu Thermal Head (FTP-040 MCSOO1), aTDK Thermal Head F415 HH₇ -1089 or a Rohm Thermal Head KE 2008-F3.

A laser may also be used to transfer dye from the dye-donor elements ofthe invention. When a laser is used, it is preferred to use adiode lasersince it offers substantial advantages in terms of its small size, lowcost, stability, reliability, ruggedness, and ease of modulation. Inpractice, before any laser can be used to heat a dye-donor element, theelement must contain an infrared-absorbing material, such as carbonblack, cyanine infrared absorbing dyes as described in U.S. Pat. No.4,973,572 or other materials as described in the following U.S.application Ser. Nos.: 367,062, 367,064, 367,061 and 369,492, and U.S.Pat. Nos. 4,948,777, 4,950,640, 4,950,639, 4,948,776, 4,948,776,4,948,778, 4,942,141, 4,952,552 and 4,912,083, the disclosures of whichare hereby incorporated by reference. The laser radiation is thenabsorbed into the dye layer and converted to heat by a molecular processknown as internal conversion. Thus, the construction of a useful dyelayer will depend not only on the hue, transferability and intensity ofthe image dyes, but also on the ability of the dye layer to absorb theradiation and convert it to heat.

Lasers which can be used to transfer dye from dye-donors employed in theinvention are available commercially. There can be employed, forexample, Laser Model SDL-2420-H₂ from Spectra Diode Labs, or Laser ModelSLD 304 V/W from Sony Corp.

A thermal printer which uses the laser described above to form an imageon a thermal print medium is described and claimed in copending U.S.application Ser. No. 451,656 of Baek and DeBoer, filed Dec. 18, 1989,the disclosure of which is hereby incorporated by reference.

Spacer beads may be employed in a separate layer over the dye layer ofthe dye-donor in the above-described laser process in order to separatethe dye-donor from the dye-receiver during dye transfer, therebyincreasing the uniformity and density of the transferred image. Thatinvention is more fully described in U.S. Pat. No. 4,772,582, thedisclosure of which is hereby incorporated by reference. Alternatively,the spacer beads may be employed in the receiving layer of thedye-receiver as described in U.S. Pat. No. 4,876,235, the disclosure ofwhich is hereby incorporated by reference. The spacer beads may becoated with a polymeric binder if desired.

The use of an intermediate receiver with subsequent retransfer to asecond receiving element may also be employed in the invention. Amultitude of different substrates can be used to prepare the color proof(the second receiver) which is preferably the same substrate used forthe printing press run. Thus, this one intermediate receiver can beoptimized for efficient dye uptake without dye-smearing orcrystallization.

Examples of substrates which may be used for the second receivingelement (color proof) include the following: Flo Kote Cove® (S. D.Warren Co.), Champion Textweb® (Champion Paper Co.), Quintessence Gloss®(Potlatch Inc.), Vintage Gloss® (Potlatch Inc.), Khrome Kote® (ChampionPaper Co.), Consolith Gloss® (Consolidated Papers Co.), Ad-Proof Paper®(Appleton Papers, Inc.) and Mountie Matte® (Potlatch Inc.).

As noted above, after the dye image is obtained on a first dye-receivingelement, it is retransferred to a second dye image-receiving element.This can be accomplished, for example, by passing the two receiversbetween a pair of heated rollers. Other methods of retransferring thedye image could also be used such as using a heated platen, use ofpressure and heat, external heating, etc.

Also as noted above, in making a color proof, a set of electricalsignals is generated which is representative of the shape and color ofan original image. This can be done, for example, by scanning anoriginal image, filtering the image to separate it into the desiredadditive primary colors-red, blue and green, and then converting thelight energy into electrical energy. The electrical signals are thenmodified by computer to form the color separation data which is used toform a halftone color proof. Instead of scanning an original object toobtain the electrical signals, the signals may also be generated bycomputer. This process is described more fully in Graphic Arts Manual,Janet Field ed., Arno Press, New York 1980 (p. 358ff), the disclosure ofwhich is hereby incorporated by reference.

A thermal dye transfer assemblage of the invention comprises

a) a dye-donor element as described above, and

b) a dye-receiving element as described above, the dye-receiving elementbeing in a superposed relationship with the dye-donor element so thatthe dye layer of the donor element is in contact with the dyeimage-receiving layer of the receiving element.

The above assemblage comprising these two elements may be preassembledas an integral unit when a monochrome image is to be obtained. This maybe done by temporarily adhering the two elements together at theirmargins. After transfer, the dye-receiving element is then peeled apartto reveal the dye transfer image.

When a three color image is to be obtained, the above assemblage isformed three times using different dye-donor elements. After the firstdye is transferred, the elements are peeled apart. A second dye-donorelement (or another area of the donor element with a different dye area)is then brought in register with the dye-receiving element and theprocess repeated. The third color is obtained in the same manner.

The following examples are provided to illustrate the invention.

EXAMPLE 1 SYNTHESIS OF COMPOUND I-1 A. Synthesis of2-phenyl-1,1,3-tricyano propene (intermediate for Compound I-1)

A mixture of benzoylacetonitrile (9.94 g, 0.0685 mole), malononitrile(11.3 g, 0.17 mole), ammonium acetate (5.4 g, 0.07 mole) and ethanol(100 mL) was heated at reflux for 1.5 hours. After cooling to roomtemperature, the reaction mixture was diluted with water (50 mL) andconcentrated hydrochloric acid (7.5 mL) was added dropwise over 5minutes. The resulting precipitate was collected by filtration andwashed with water and ligroin. The yield was 10.0 g (76%), m.p. 92°-98°C.

B. Synthesis of Compound I-1: 2-phenyl1,1,3-tricyano-3-(4-diethylamino-2-methylphenylimino)-propene ##STR21##

A mixture of the phenyltricyanopropene above (0.58 g, 0.003 mole) and2-amino-5-diethylaminotoluene hydrochloride (0.64 g, 0.003 mole) in asolution of methanol (30 mL) and water (10 mL) was treated withconcentrated ammonium hydroxide (1.8 mL). To this mixture was slowlyadded a solution of potassium ferricyanide (4.94 g, 0.015 mole) in water(20 mL), keeping the temperature below 20° C. with external cooling.After stirring for 2 hours, the reaction mixture was diluted with water(100 mL) and the resulting precipitate was collected by filtration andwashed well with water. The crude dye was crystallized from methanol toyield 0.85 g (81%) of a dark green powder. The dye had a lambda max of604 nm with a molar extinction coefficient of 44,200 (in acetonesolution).

EXAMPLE 2

A black dye-donor element was prepared by coating on a 100 μmpoly(ethylene terephthalate) support:

1) a subbing layer of poly(acrylonitrile-co-vinylidene chlorideco-acrylic acid) (0.054 g/m²) (14:79:7 wt. ratio); and

2) a dye layer containing a mixture of cyan dye I-1, yellow dye II-1 andmagenta dye III-1 illustrated above, (total dye coverage of 0.65g/m²)and the cyanine infrared absorbing dye illustrated below (0.054 g/m²) ina cellulose acetate propionate binder (2.5% acetyl, 45% propionyl) (0.27g/m²) coated from dichloromethane.

Other dye donors according to the invention were prepared as aboveexcept using the dyes identified below in the Table and illustratedabove. Comparison dye-donors using a mixture of cyan, yellow and magentadyes of the prior art as identified below, at a total coverage of 0.65g/m², were also prepared similar to the dye-donor described above.

Cyanine Infrared Absorbing Dye ##STR22##

An intermediate dye-receiving element was prepared by coating on anunsubbed 100 μm thick poly(ethylene terephthalate) support a layer ofcrosslinked poly(styrene-co-divinylbenzene) beads (14 micron averagediameter) (0.11 g/m²), triethanolamine (0.09 g/m²) and DC-510® SiliconeFluid (Dow Corning Company) (0.01 g/m²) in a Butvar® 76 binder, apoly(vinyl alcohol-co-butyral), (Monsanto Company) (4.0 g/m²) from1,1,2-trichloroethane or dichloromethane.

Single color images were printed as described below from dye-donors ontoa receiver using a laser imaging device as described in U.S. Pat. No.4,876,235. The laser imaging device consisted of a single diode laserconnected to a lens assembly mounted on a translation stage and focusedonto the dye-donor layer.

The dye-receiving element was secured to the drum of the diode laserimaging device with the receiving layer facing out. The dye-donorelement was secured in face-to-face contact with the receiving element.

The diode laser used was a Spectra Diode Labs No. SDL-2430-H₂, having anintegral, attached optical fiber for the output of the laser beam, witha wavelength of 816 nm and a nominal power output of 250 milliwatts atthe end of the optical fiber. The cleaved face of the optical fiber (100microns core diameter) was imaged onto the plane of the dye-donor with a0.33 magnification lens assembly mounted on a translation stage giving anominal spot size of 33 microns and a measured power output at the focalplane of 115 milliwatts.

The drum, 312 mm in circumference, was rotated at 500 rpm and theimaging electronics were activated. The translation stage wasincrementally advanced across the dye-donor by means of a lead screwturned by a microstepping motor, to give a center-to-center linedistance of 14 microns (714 lines per centimeter, or 1800 lines perinch). For a continuous tone stepped image, the current supplied to thelaser was modulated from full power to 16% power in 4% increments.Maximum transfer density can be increased at the expense of printingspeed by slowing the drum rotation while keeping all other operatingparameters constant.

After the laser had scanned approximately 12 mm, the laser exposingdevice was stopped and the intermediate receiver was separated from thedye donor. The intermediate receiver containing the stepped dye imagewas laminated to Ad-Proof Paper® (Appleton Papers, Inc.) 60 pound stockpaper by passage through a pair of rubber rollers heated to 120° C. Thepolyethylene terephthalate support was then peeled away leaving the dyeimage and polyvinyl alcohol-co-butyral firmly adhered to the paper. Thepaper stock was chosen to represent the substrate used for a printed inkimage obtained from a printing press.

The Status T density of each of the stepped images was read using anX-Rite® 418 Densitometer to find the single step image within 0.05density unit of the SWOP Color Reference. For the black standard, thisdensity was 1.6.

The a* and b* values of the selected step image of transferreddye-mixture was compared to that of the SWOP Color Reference by readingon an X-Rite® 918 Colorimeter set for D50 illuminant and a 10 degreeobserver. The L* reading was checked to see that it did not differappreciably from the reference. The a* and b* readings were recorded andthe distance from the SWOP Color Reference calculated as the square rootof the sum of differences squared for a* and b*: ##EQU1## e=experiment(transferred dye) s=SWOP Color Reference

In addition, the above dye-donors were evaluated for storage stabilityby comparing transmission spectra of the donor before and afterincubation at 50° C./50% RH for 4 days.

The following results were obtained:

                                      TABLE 1                                     __________________________________________________________________________    Dyes            Distance Density @                                                                             Storage                                      (Weight Ratio)                                                                        a*  b*  From Reference                                                                         500 rpm Stability                                    __________________________________________________________________________    SWOP    1.5 2.0 --       --      --                                           I-1/II-1/III-1                                                                        4.5.sup.a                                                                         2.sup.a                                                                           3        1.2     no change                                    (18:26:16)                                                                    I-8/II-1/III-19                                                                       1.5 1.0 1        1.9     no change                                    (21:25:14)                                                                    I-8/II-1/III-1                                                                        -1.5                                                                              1.0 3        1.8     no change                                    (20:24:16)                                                                    Control 1.sup.b                                                                       -1.2.sup.c                                                                        -5.4.sup.c                                                                        8.0      0.8     no change                                    Control 2.sup.d                                                                       -2.4                                                                              -1.5                                                                              5.5      1.6     75% of cyan component                                                         decomposed; magenta dye                                                       sublimes from coating at                                                      room temperature                             Control 3.sup.e                                                                       -6.4                                                                              -2.1                                                                              9        1.7     30% of cyan component                                                         decomposed                                   __________________________________________________________________________     .sup.a In order to obtain sufficient density for colorimetric comparisons     the laser imaging device had to be slowed to 450 rpm.                         .sup.b Similar to Example C17, Table C17, from U.S. Pat. No. 4,923,846, a     mixture of Solvent Blue 36, Solvent Red 19 and Foron Brilliant Yellow S6G     (structures below) in a ratio of 7:4:4.                                        .sup.c In order to obtain sufficient density for colorimetric                comparisons, the laser imaging device had to be slowed to 400 rpm.            .sup.d Similar to Example 1 of U.S. Pat. No. 4,186,435, a mixture of dyes     C1, C3 and C5 in a 32:12.5:15.5 ratio (structures below)                      .sup.e Similar to Example 3 of JP 01/136,787, a mixture of dyes C6, C4, C     and C1 (structures below) in a 2:3:3:2 ratio.                                 ##STR23##

The data in the Table show that the dye combination of the inventionprovides high transfer density, neutral black hue very close to the SWOPColor Reference and excellent donor storage stability. The dyes of theprior art are further away from the SWOP Color Reference. In addition,the dyes disclosed in U.S. Pat. No. 4,923,846 are not capable ofyielding high transfer density while the dyes of U.S. Pat. No. 4,186,435and JP01-136787 exhibit very poor storage stability.

The invention has been described in detail with particular reference topreferred embodiments thereof, but it will be understood that variationsand modifications can be effected within the spirit and scope of theinvention.

What is claimed is:
 1. A black dye-donor element for thermal dyetransfer comprising a support having thereon a dye layer comprising amixture of at least one cyan, magenta and yellow dyes dispersed in apolymeric binder, at least one of the cyan dyes having the formula:##STR24## wherein: R¹ and R² each independently represents hydrogen; asubstituted or unsubstituted alkyl group having from 1 to about 10carbon atoms; a substituted or unsubstituted cycloalkyl group havingfrom about 5 to about 7 carbon atoms or a substituted or unsubstitutedallyl group; with the proviso that R¹ and R² cannot both be hydrogen; orR¹ and R² can be joined together to form, along with the nitrogen towhich they are attached, a 5- to 7-membered heterocyclic ring;or eitheror both of R¹ and R² can be combined with an R³ to form a 5- to7-membered heterocyclic ring; each R³ independently representssubstituted or unsubstituted alkyl, cycloalkyl or allyl as describedabove for R¹ and R², alkoxy, aryloxy, halogen, thiocyano, acylamido,ureido, alkylsulfonamido, arylsulfonamido, alkylthio, arylthio ortrifluoromethyl; or any two of R³ may be combined together to form a 5-or 6-membered carbocyclic or heterocyclic ring; or one or two of R³ maybe combined with either or both of R¹ and R² to complete a 5- to7-membered ring; m is an integer of from 0 to 4; R⁴ represents hydrogenor an electron withdrawing group; R⁵ represents an electron withdrawinggroup, a substituted or unsubstituted aryl group having from about 6 toabout 10 carbon atoms or a substituted or unsubstituted hetaryl grouphaving from about 5 to about 10 atoms; R⁶ and R⁷ each independentlyrepresents an electron withdrawing group; and R⁶ and R⁷ may be combinedto form the residue of an active methylene compound;and at least one ofthe yellow dyes having the formula: ##STR25## wherein: R⁸ represents thesame groups as R¹ above; a substituted or unsubstituted aryl group offrom about 6 to about 10 carbon atoms; a substituted or unsubstitutedhetaryl group of from about 5 to about 10 atoms; R⁹ and R¹⁰ eachindependently represents hydrogen; R⁸ ; cyano; acyloxy; alkoxy of 1 toabout 6 carbon atoms; halogen; or alkoxy carbonyl; or any two of R⁸, R⁹and R¹⁰ together represent the atoms necessary to complete a 5- to7-membered ring; R¹¹ represents the same groups as R⁸ ; G represents asubstituted or unsubstituted alkyl, cycloalkyl or allyl group asdescribed above for R⁸, NR¹² R¹³ or OR¹⁴ ; R¹² and R¹³ eachindependently represents hydrogen, acyl or R⁸, with the proviso that R¹²and R¹³ cannot both be hydrogen at the same time; or R¹² and R¹³together represent the atoms necessary to complete a 5- to 7-memberedring; R¹⁴ represents alkyl, cycloalkyl or allyl groups as in R¹ above,or aryl or hetaryl as in R⁸ above; X represents C(R¹⁸)(R¹⁹), S, O orNR¹⁸ ; R¹⁸ and R¹⁹ each independently represents the same groups as R⁸ ;or R¹⁸ and R¹⁹ together represent the atoms necessary to complete a 5-to 7-membered ring; and Y represents the atoms necessary to complete a5- or 6-membered ring which may be fused to another ring system;and atleast one of the magenta dyes having the formula: ##STR26## wherein: R¹⁵represents hydrogen or a substituted or unsubstituted alkyl or allylgroup of from 1 to about 10 carbon atoms; Q is R¹⁵, an alkoxy group offrom 1 to about 4 carbon atoms or taken together with R¹⁶ represents theatoms which form a 5- or 6-membered heterocyclic ring; R¹⁶ is asubstituted or unsubstituted alkyl or allyl group of from 1 to about 10carbon atoms, or can be combined with Q as described above; R²⁰ is asubstituted or unsubstituted alkyl group of from 1 to about 10 carbonatoms or a substituted or unsubstituted aryl group of from about 6 toabout 10 carbon atoms; J is CO, CO₂, --SO₂ -- or CONR²¹ --; R¹⁷ is asubstituted or unsubstituted alkyl or allyl group of from 1 to about 10carbon atoms or a substituted or unsubstituted aryl group of from about6 to about 10 carbon atoms; and R²¹ is hydrogen or R²⁰.
 2. The elementof claim 1 wherein R⁴, R⁶ and R⁷ in formula I are cyano.
 3. The elementof claim 1 wherein R¹ in formula I is C₂ H₅, C₂ H₄ OH, or n-C₃ H₇. 4.The element of claim 1 wherein R² in formula I is C₂ H₅ or n-C₃ H₇. 5.The element of claim 1 wherein R³ in formula I is hydrogen, OC₂ H₅, CH₃or NHCOCH₃.
 6. The element of claim 1 wherein R⁵ in formula I is p-C₆ H₄Cl, m-C₆ H₄ NO₂ or naphthyl.
 7. The element of claim 1 wherein G isN(CH₃)₂ or CH₃.
 8. The element of claim 1 wherein X is C(CH₃)₂ or O. 9.The element of claim 1 wherein R⁸ is C₂ H₅ or CH₃ and R¹¹ is C₆ H₅. 10.The element of claim 1 wherein R⁹ and R¹⁰ are each hydrogen.
 11. Theelement of claim 1 wherein R¹⁵ and R¹⁶ are each C₃ H₇, Q is H, J is CO,R²⁰ is CH₃ and R¹⁷ is 3-CH₂ CO₂ C₂ H₅.
 12. The element of claim 1wherein R¹⁵ and R¹⁶ are each C₃ H₇, Q is H, J is CO, R²⁰ is CH₃ and R¹⁷is CH₂ CH=CH₂.
 13. The element of claim 1 wherein said dye-donor elementcontains an infrared-absorbing dye in said dye layer.
 14. In a processof forming a dye transfer image comprising imagewise-heating a blackdye-donor element comprising a support having thereon a dye layercomprising a mixture of at least one cyan, magenta and yellow dyesdispersed in a polymeric binder, at least one of the cyan dyes havingthe formula: ##STR27## wherein: R¹ and R² each independently representshydrogen; a substituted or unsubstituted alkyl group having from 1 toabout 10 carbon atoms; a substituted or unsubstituted cycloalkyl grouphaving from about 5 to about 7 carbon atoms or a substituted orunsubstituted allyl group; with the proviso that R¹ and R² cannot bothbe hydrogen;or R¹ and R² can be joined together to form, along with thenitrogen to which they are attached, a 5- to 7- membered heterocyclicring; or either or both of R¹ and R² can be combined with an R³ to forma 5- to 7-membered heterocyclic ring; each R³ independently representssubstituted or unsubstituted alkyl, cycloalkyl or allyl as describedabove for R¹ and R², alkoxy, aryloxy, halogen, thiocyano, acylamido,ureido, alkylsulfonamido, arylsulfonamido, alkylthio, arylthio ortrifluoromethyl; or any two of R³ may be combined together to form a 5-or 6-membered carbocyclic or heterocyclic ring; or one or two of R³ maybe combined with either or both of R¹ and R² to complete a 5- to7-membered ring; m is an integer of from 0 to 4; R⁴ represents hydrogenor an electron withdrawing group; R⁵ represents an electron withdrawinggroup, a substituted or unsubstituted aryl group having from about 6 toabout 10 carbon atoms or a substituted or unsubstituted hetaryl grouphaving from about 5 to about 10 atoms; R⁶ and R⁷ each independentlyrepresents an electron withdrawing group; and R⁶ and R⁷ may be combinedto form the residue of an active methylene compound;and at least one ofthe yellow dyes having the formula: ##STR28## wherein: R⁸ represents thesame groups as R¹ above; a substituted or unsubstituted aryl group offrom about 6 to about 10 carbon atoms; a substituted or unsubstitutedhetaryl group of from about 5 to about 10 atoms; R⁹ and R¹⁰ eachindependently represents hydrogen; R⁸ ; cyano; acyloxy; alkoxy of 1 toabout 6 carbon atoms; halogen; or alkoxy carbonyl; or any two of R⁸, R⁹and R¹⁰ together represent the atoms necessary to complete a 5- to7-membered ring; R¹¹ represents the same groups as R⁸ ; G represents asubstituted or unsubstituted alkyl, cycloalkyl or allyl group asdescribed above for R⁸, NR¹² R¹³ or OR¹⁴ ; R¹² and R¹³ eachindependently represents hydrogen, acyl or R⁸, with the proviso that R¹²and R¹³ cannot both be hydrogen at the same time; or R¹² and R¹³together represent the atoms necessary to complete a 5- to 7l-memberedring; R¹⁴ represents alkyl, cycloalkyl or allyl groups as in R¹ above,or aryl or hetaryl as in R⁸ above; X represents C(R¹⁸)(R¹⁹), S, O orNR¹⁸ ; R¹⁸ and R¹⁹ each independently represents the same groups as R⁸ ;or R¹⁸ and R¹⁹ together represent the atoms necessary to complete a 5-to 7-membered ring; and Y represents the atoms necessary to complete a5l- or 6-membered ring which may be fused to another ring system;and atleast one of the magenta dyes having the formula: ##STR29## wherein: R¹⁵represents hydrogen or a substituted or unsubstituted alkyl or allylgroup of from 1 to about 10 carbon atoms; Q is R¹⁵, an alkoxy group offrom 1 to about 4 carbon atoms or taken together with R¹⁶ represents theatoms which form a 5- or 6-membered heterocyclic ring; R¹⁶ is asubstituted or unsubstituted alkyl or allyl group of from 1 to about 10carbon atoms, or can be combined with Q as described above; R²⁰ is asubstituted or unsubstituted alkyl group of from 1 to about 10 carbonatoms or a substituted or unsubstituted aryl group of from about 6 toabout 10 carbon atoms; J is CO, CO₂, --SO₂ -- or CONR²¹ --; R¹⁷ is asubstituted or unsubstituted alkyl or allyl group of from 1 to about 10carbon atoms or a substituted or unsubstituted aryl group of from about6 to about 10 carbon atoms; and R²¹ is hydrogen or R²⁰.
 15. The processof claim 14 wherein said dye-donor element contains aninfrared-absorbing dye in said dye layer.
 16. In a thermal dye transferassemblage comprising:a) a black dye-donor element comprising a supporthaving thereon a dye layer comprising a mixture of cyan, yellow andmagenta dyes dispersed in a polymeric binder, and b) a dye-receivingelement comprising a support having thereon a dye image-receiving layer,said dye-receiving element being in a superposed relationship with saidblack dye-donor element so that said dye layer is in contact with saiddye image-receiving layer, the improvement wherein at least one of thecyan dyes has the formula: ##STR30## wherein: R¹ and R² eachindependently represents hydrogen; a substituted or unsubstituted alkylgroup having from 1 to about 10 carbon atoms; a substituted orunsubstituted cycloalkyl group having from about 5 to about 7 carbonatoms or a substituted or unsubstituted allyl group; with the provisothat R¹ and R² cannot both be hydrogen;or R¹ and R² can be joinedtogether to form, along with the nitrogen to which they are attached, a5- to 7-membered heterocyclic ring; or either or both of R¹ and R² canbe combined with an R³ to form a 5- to 7-membered heterocyclic ring;each R³ independently represents substituted or unsubstituted alkyl,cycloalkyl or allyl as described above for R¹ and R², alkoxy, aryloxy,halogen, thiocyano, acylamido, ureido, alkylsulfonamido,arylsulfonamido, alkylthio, arylthio or trifluoromethyl; or any two ofR³ may be combined together to form a 5- or 6-membered carbocyclic orheterocyclic ring; or one or two of R³ may be combined with either orboth of R¹ and R² to complete a 5- to 7-membered ring; m is an integerof from 0 to 4; R⁴ represents hydrogen or an electron withdrawing group;R⁵ represents an electron withdrawing group, a substituted orunsubstituted aryl group having from about 6 to about 10 carbon atoms ora substituted or unsubstituted hetaryl group having from about 5 toabout 10 atoms; R⁶ and R⁷ each independently represents an electronwithdrawing group; and R⁶ and R⁷ may be combined to form the residue ofan active methylene compound; and at least one of the yellow dyes havingthe formula: ##STR31## wherein: R⁸ represents the same groups as R¹above; a substituted or unsubstituted aryl group of from about 6 toabout 10 carbon atoms; a substituted or unsubstituted hetaryl group offrom about 5 to about 10 atoms;R⁹ and R¹⁰ each independently representshydrogen; R⁸ ; cyano, acyloxy; alkoxy of 1 to about 6 carbon atoms;halogen; or alkoxycarbonyl; or any two of R⁸, R⁹ and R¹⁰ togetherrepresent the atoms necessary to complete a 5- to 7-membered ring; R¹¹represents the same groups as R⁸ ; G represents a substituted orunsubstituted alkyl, cycloalkyl or allyl group as described above forR⁸, NR¹² R¹³ or OR¹⁴ ; R¹² and R¹³ each independently representshydrogen, acyl or R⁸, with the proviso that R¹² and R¹³ cannot both behydrogen at the same time; or R¹² and R¹³ together represent the atomsnecessary to complete a 5- to 7-membered ring; R¹⁴ represents alkyl,cycloalkyl or allyl groups as in R¹ above, or aryl or hetaryl as in R⁸above; X represents C(R¹⁸)(R¹⁹), S, O or NR¹⁸ ; R¹⁸ and R¹⁹ eachindependently represents the same groups as R⁸ ; or R¹⁸ and R¹⁹ togetherrepresent the atoms necessary to complete a 5- to 7-membered ring; and Yrepresents the atoms necessary to complete a 5- or 6-membered ring whichmay be fused to another ring system; and at least one of the magentadyes having the formula: ##STR32## wherein: R¹⁵ represents hydrogen or asubstituted or unsubstituted alkyl or allyl group of from 1 to about 10carbon atoms;Q is R¹⁵, an alkoxy group of from 1 to about 4 carbon atomsor taken together with R¹⁶ represents the atoms which form a 5- or6-membered heterocyclic ring; R¹⁶ is a substituted or unsubstitutedalkyl or allyl group of from 1 to about 10 carbon atoms, or can becombined with Q as described above; R²⁰ is a substituted orunsubstituted alkyl group of from 1 to about 10 carbon atoms or asubstituted or unsubstituted aryl group of from about 6 to about 10carbon atoms; J is CO, CO₂, --SO₂ -- or CONR²¹ --; R¹⁷ is a substitutedor unsubstituted alkyl or allyl group of from 1 to about 10 carbon atomsor a substituted or unsubstituted aryl group of from about 6 to about 10carbon atoms; and R²¹ is hydrogen or R²⁰.
 17. The assemblage of claim 16wherein said dye-donor element contains an infrared-absorbing dye insaid dye layer.